בא

One of the instructions to the Israelites was to request vessels from the Egyptians prior to their departure from Egypt and to take the vessels with them. The Sages explain that God promised Abraham that after the exile, his descendants would emerge with great wealth, and He must keep His word. 

“Speak now [na] in the ears of the people and they shall ask each man from his neighbor and each woman from her neighbor, silver vessels and gold vessels” (Exodus 11:2). The Sages said in the study hall of Rabbi Yannai: “Na” is an expression of nothing other than entreaty. The Holy One, blessed be He, said to Moses: I entreat you, go and say to the Israelites: I entreat you, request from the Egyptians silver vessels and gold vessels, so that righteous man, Abraham, will not say: You fulfilled concerning them that which You told me: “And they will be enslaved to them and they will oppress them” (Genesis 15:13), but You did not fulfill concerning them that which You told me: “And afterward they will emerge with great property” (Genesis 15:14). The Israelites said to Moses: It would be enough if we ourselves depart Egypt, [even without wealth]. This can be compared to a man who was incarcerated in prison, and people would say to him: Tomorrow they are releasing you from prison and giving you much property. He says to them: I entreat you, release me today, and I request nothing. <source>(Berakhot 9a) </source>